Sub-atomic particles; Thomson and Rutherford models — NEET & JEE Questions

Question 1 · difficulty L1 · recall

The neutron was discovered in 1932 by bombarding a thin sheet of beryllium with alpha particles. The scientist credited with this discovery is

• A. J.J. Thomson
• B. E. Goldstein
• C. James Chadwick
• D. R.A. Millikan

Question 2 · difficulty L2 · understanding

The number of following statement/s which is/are incorrect is ___________ (A) Line emission spectra are used to study the electronic structure (B) The emission spectra of atoms in the gas phase show a continuous spread of wavelength from red to violet (C) An absorption spectrum is like the photographic negative of an emission spectrum (D) The element helium was discovered in the sun by spectroscopic method

Question 3 · difficulty L2 · understanding

The incorrect postulates of the Dalton's atomic theory are : (A) Atoms of different elements differ in mass. (B) Matter consists of divisible atoms. (C) Compounds are formed when atoms of different element combine in a fixed ratio. (D) All the atoms of given element have different properties including mass. (E) Chemical reactions involve reorganisation of atoms. Choose the correct answer from the options given below :

• A. (B), (D) only
• B. (A), (B), (D) only
• C. (B), (D), (E) only
• D. (C), (D), (E) only

Question 4 · difficulty L2 · understanding

Choose the Incorrect Statement about Dalton's Atomic Theory

• A. Compounds are formed when atoms of different elements combine in any ratio.
• B. Matter consists of indivisible atoms.
• C. chemical reactions involve reorganization of atoms
• D. All the atoms of a given element have identical properties including identical mass.

Question 5 · difficulty L2 · understanding

If the Thompson model of the atom was correct, then the result of Rutherford's gold foil experiment would have been :

• A. All of the $$\alpha$$-particles pass through the gold foil without decrease in speed.
• B. $$\alpha$$-particles are deflected over a wide range of angles.
• C. All $$\alpha$$-particles get bounced back by 180$$^\circ$$
• D. $$\alpha$$-particles pass through the gold foil deflected by small angles and with reduced speed.

Question 6 · difficulty L3 · understanding

Given below are two statements : Statement I : Rutherford's gold foil experiment cannot explain the line spectrum of hydrogen atom. Statement II : Bohr's model of hydrogen atom contradicts Heisenberg' uncertainty principle. In the light of the above statements, choose the most appropriate answer from the options given below :

• A. Statement I is false but statement II is true.
• B. Statement I is true but statement II is false.
• C. Both statement I and statement II are false.
• D. Both statement I and statement II are true.

Question 7 · difficulty L3 · understanding

Select the correct Statements from the following : A. Atoms of all elements are composed of two fundamental particles. B. The mass of the electron is $$9.10939 \times 10^{-31} \mathrm{~kg}$$. C. All the isotopes of a given elements show same chemical properties. D. Protons and electrons are collectively known as nucleons. E. Dalton's atomic theory, regarded the atom as an ultimate particle of matter. Choose the correct answer from the options given below.

• A. C, D and E only
• B. A and E only
• C. B, C and E only
• D. A, B and C only

Question 8 · difficulty L3 · application

The charge-to-mass ratio of the electron is 1.758820 x 10$^{11}$ C kg$^{-1}$ and its charge is 1.6022 x 10$^{-19}$ C. The mass of the electron is approximately

• A. 1.67 x 10$^{-27}$ kg
• B. 2.82 x 10$^{-8}$ kg
• C. 9.11 x 10$^{-28}$ kg
• D. 9.11 x 10$^{-31}$ kg

Question 9 · difficulty L3 · application

A species has 20 protons, 20 neutrons and 18 electrons. Which symbol represents it correctly?

• A. $^{40}_{20}$Ca$^{2+}$
• B. $^{40}_{18}$Ar
• C. $^{38}_{20}$Ca$^{2+}$
• D. $^{40}_{20}$Ca$^{2-}$

Question 10 · difficulty L4 · application

In Rutherford's alpha-particle scattering experiment, three observations were made. Which option pairs each observation with the correct conclusion?

• A. Most pass undeflected - the atom has no positive charge; a few deflect - electrons are heavy; very few bounce back - the foil is thick
• B. Most alpha particles pass undeflected - most of the space in the atom is empty; a few deflect by small angles - the positive charge is concentrated in a very small volume; very few (about 1 in 20,000) bounce back - the nucleus is tiny compared with the atom, its radius about 10$^{-15}$ m against 10$^{-10}$ m for the atom
• C. Most pass undeflected - the positive charge is spread uniformly; a few deflect - the nucleus is large; very few bounce back - alpha particles are negative
• D. All three observations show that the mass is uniformly distributed